The present invention relates to a washer pump preferable for a washer device that sprays cleaning liquid to the windshield of a vehicle. More specifically, the present invention relates to a motor brush support structure preferable for washer pump.
A typical washer device for vehicles includes a tank for storing cleaning liquid and a washer pump for pumping the cleaning liquid from the tank to a washer nozzle. A washer pump described in Japanese Unexamined Patent Publication 4-129863 has a housing including a motor chamber and a pump chamber. The motor chamber accommodates a direct current motor. The pump chamber includes an impeller. The motor rotates the impeller, which pumps the cleaning liquid from the tank to the washer nozzle.
Compact and light vehicle washer devices are preferred. To reduce the size and weight of a washer device, it is necessary to reduce the size and weight of the motor since the motor accounts for a large portion of the weight of the washer pump. However, simply reducing the size of the motor reduces the torque and lowers the performance of the washer pump.
To reduce the size and weight of the motor without producing the torque, a flattened motor is desired. In detail, the cross section of the motor is preferably shaped as if two opposite sides of a circle were cut off. Such motors are described in Japanese Unexamined Patent Publication No. 4-129863, Japanese Unexamined Utility Model Publication No. 61-43768, Japanese Unexamined Utility Model Publication No. 6-52370, and Japanese Unexamined Utility Model Publication No. 4-111263. Each motor described in any one of these publications includes a pair of opposed arcuate portions and a pair of opposed flat portions.
The motor includes an armature and a commutator that are located on the output shaft, a pair of magnets surrounding the armature, a pair of brushes contacting the commutator, and a pair of supports for the brushes. Publication No. 61-43768 and 6-52370 describe a support including a plate spring. The plate spring includes a proximal end supported by the lid of the motor case and a distal end on which the brush is fixed. The resilience of the plate spring presses the brush against the commutator.
The brush contact pressure to the commutator greatly influences the operational losses of the motor, such as resistance loss and friction loss. Therefore, the brush contact pressure to the commutator must be properly maintained. However, as the brush wears, the force of the plate spring supporting the brush changes, which changes the brush contact pressure.
To minimize the change of force of the plate spring due to wear of the brush, it is necessary to maximize the distance between the fixed end of the plate spring and the brush at the distal end of the plate spring. In other words, it is necessary to maximize the length of the arm portion of the plate spring. The longer the arm portion of the plate spring is, the smaller the change of the plate spring force due to brush wear is. In this way, the initial performance of the motor can be maintained for a relatively long period.
However, in the motor described in the publications 61-43768 and 6-52370, the arm portion of the plate spring is perpendicular to the flat surfaces of the motor. The distance between the opposite flat surfaces is relatively small. Therefore, it is impossible to greatly increase the length of the arm portion of the plate spring. In other words, the size of the motor cannot be reduced by further flattening the motor without reducing the length of the arm portion of the plate spring. Accordingly, the arrangement of the plate spring shown in the publications is an obstacle to reducing the size of the motor.
In the motor described in the publications 61-43768 and 6-52370, a pair of plate springs are fixed to the lid of the motor case. The brushes on the plate springs are arranged to surround the commutator. To install the commutator between the brushes when assembling the motor, a worker must separate the plate springs from one another. This complicates the motor assembly.
In the motor described in the publication 6-52370, the input terminal that is connected to the external output terminal is attached to the lid of the motor case. The support for the brushes is attached to the lid to contact the input terminal. However, the input terminal and the support are independent and are respectively attached to the lid, which not only complicates the motor structure but limits miniaturization of the motor.
An objective of the present invention is to provide a motor brush support structure that can downsize the motor and maintain the initial performance of the motor for a relatively long period.
Another objective of the present invention is to provide a motor brush support structure that facilitates the motor assembly.
A still further objective of the present invention is to provide a washer pump including such a motor brush support structure.
To achieve the above objectives, the present invention provides a motor brush support structure. The motor includes a case having a detachable lid, an output shaft, and a commutator located on the output shaft. The support structure comprises a brush, a resilient member, a base and an engagement structure. The brush is opposed to the commutator. The resilient member urges the brush toward the commutator such that the brush contacts the commutator. The base is attached to the lid. The base includes a retainer for retaining the resilient member. The engagement structure is located between the resilient member and the retainer such that the resilient member is detachably secured to the retainer.
In a motor brush support structure provided by the another aspect of the present invention, the motor includes a case, an output shaft, and a commutator located on the output shaft. The case has a flat wall located inward of an imaginary circle circumscribing the case. The support structure comprises a brush and a resilient member. The brush is opposed to the commutator. The resilient member urges the brush toward the commutator such that the brush contacts the commutator. The resilient member includes a fixed portion supported by the case and a resilient arm portion to which the brush is fixed. The resilient arm portion extends from the fixed portion such that the resilient arm portion is substantially perpendicular to the output shaft and is substantially parallel to the flat wall.
Also, the present invention provides a pump. The pump comprises a housing, which includes a motor chamber, an impeller, which draws in and pumps out liquid, and a motor, which is accommodated in the motor chamber to drive the impeller. The motor includes a case, which has a flat wall located inward of an imaginary circle circumscribing the case, an output shaft, which is coupled to the impeller, a commutator, which is located on the output shaft, a brush, which is opposed to the commutator, and a resilient member, which urges the brush toward the commutator such that the brush contacts the commutator. The resilient member includes a fixed portion supported by the case and a resilient arm portion to which the brush is fixed. The resilient arm portion extends from the fixed portion such that the resilient arm portion is substantially perpendicular to the output shaft and is substantially parallel to the flat wall.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.